Cloud-Radiative Impact on the Dynamics of Extratropical Cyclones during NAWDEX

Abstract Cloud-radiative heating (CRH) affects the dynamics of extratropical cyclones and near-tropopause circulations. Previous studies on the impact of CRH were mostly limited to simulations of idealized baroclinic life cycles. To bridge the gap between idealized studies and practical applications, we investigate the impact of CRH on the dynamics of extratropical cyclones. Using the Icosahedral Nonhydrostatic (ICON) model, we simulate four cyclones during the North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) field campaign and apply the Clouds On–Off Klimate Model Intercomparison Experiment (COOKIE) method to compare simulations with and without CRH. We find that CRH systematically affects latent heating, vertical motion, and precipitation rates within the ascending regions of the cyclones and that the impact of CRH is more prominent at upper levels. Furthermore, we investigate the impact of CRH on near-tropopause dynamics by diagnosing the evolution of differences in potential vorticity (PV). Consistent with idealized studies, CRH affects extratropical cyclones and PV near the tropopause mainly through changes in latent heating and subsequently through changes in the divergent and rotational flows. The impact of CRH can vary over time and depend on the large-scale flow configuration. Finally, we perform simulations with different ice optical parameterizations and radiation solvers. These simulations show that uncertainties in CRH can indeed affect the evolution of cyclones and PV near the tropopause. Our results emphasize the need to better understand the impact of CRH and to improve its representation in numerical weather prediction models.